When I got the news about Israel’s armed attack on the Gaza Flotilla at 2:30 a.m. May 31, I felt sick. I immediately called a friend in Jerusalem, one of the most committed activists I know.

Across the ocean, I could hear in her voice that she was in tears. “The worst part about it,” she said, “is that nothing will change.”

“No,” I replied. “I can’t believe that can be true. Things have to change.”

“Well,” she said, “then it is up to you, the internationals.”

She’s right. It is up to us, the internationals both here in the United States and abroad. That is why I want you to send a message to U.S. President Obama if you live outside of the United States, and to Obama and the U.S. Congress if you are a U.S. resident, demanding the immediate release of the detained human rights activists, an end to the siege on Gaza, an impartial investigation of the attack on the flotilla, and a suspension of U.S. aid until Israel abides by international law.

We still don’t know a lot about what happened to the flotilla of boats carrying some 700 human rights activists from around the world and over 10 tons of humanitarian aid to Gaza – Israel has kept the activists under a near total media blackout while sharing only its implausible narrative of events.

What we do know is that Israeli commandos boarded a ship in international waters and killed at least 10 activists, injuring dozens of others.

Israel insists that highly trained commandos were forced to fire lethally on activists, creating a new definition of self-defense. In the first alternative accounts to appear, an Israeli Knesset member and an Al Jazeera cameraman who were on board the ship at the time each described something different, a scene of chaos with civilians waving white flags and commandos using stun guns, rubber bullets and tear gas. Regardless of what actually happened when armed soldiers landed, Israel’s wanton killing of civilians is unacceptable.

We still don’t know the names of those who were killed or injured, or where they are from. And we don’t know the whereabouts or well-being of more than 400 activists still being held by Israel.

These deaths and the attacks on the boats, have hit all of us around the world particularly hard. There were people from 40 different countries on board the ships, including Israelis and Palestinians. Israel sent armed commandos onto a civilian ship in international waters, a brazenly illegal act to enforce Israel’s nearly 3-year illegal siege of Gaza – a siege that has left 1.5 million men, women and children living like prisoners on substandard diets.

The flotilla wasn’t just about this one delivery of aid. It was about the right of Palestinians to have sea, land and air routes to the rest of the world and for the need to end the blockade.

I know that there comes a point in one’s life when you simply have to take a stand. You cannot sit by silently and watch ongoing and wholly unjustified destruction of life, tacitly supported by governments around the world, and simply do nothing.

Now, as citizens of the world, we owe it to the people of Palestine, and the people of Israel who want to live in peace, and the brave people on that flotilla, to build the movement to make Israel accountable to international law and standards of simple human decency – especially because our governments have failed us.

The response of the U.S. government thus far has been wholly inadequate, with a mild statement “regretting the loss of life,” without assigning any blame for the fiasco, let alone applying any sanctions for Israel’s acts. Please, join me in telling President Obama and Congress enough is enough.

Rebecca Vilkomerson is the executive director for the Jewish Voice for Peace.